1. Field of the Invention
This invention relates to an easy open type container wherein an opening is tightly sealed with a closure member made of at least a metallic foil and a pull-opening member is provided having an initial end portion connected to a pulling tab which is connected more firmly to an upper surface of the closure member than the tearing strength of the closure member. In this manner, the closure member can be torn open by way of the pull-opening member by pulling the pulling tab upwards in relation to the closure member.
2. Description of Background Art
As for a container of this kind, there has been hitherto proposed by the inventors of the present invention a closure as shown in FIGS. 7 and 8 disclosed, for instance, in Japanese Unexamined Utility Model Registration Application Publication Showa No. 57 (1982)-177932. A closure member a shown in FIGS. 7 and 8 is made of a single layer of metallic foil such as an aluminum foil or the like or a composite layer of lamination comprising metallic foil and a thermoplastic synthetic resin layer. The closure member a is applied to cover an opening of a container barrel body c and is affixed, by curling fastening or fusion adhesion, to an annular edge of the opening of the container barrel body c through a ring-shaped member b which is made of metal or synthetic resin. A pull-opening member f comprising an annular strip member made of thermoplastic synthetic resin or the like and having at its initial end portion a pulling tab e is affixed more firmly than a tearing strength of the closure member a to an area of an upper surface of the closure member a positioned inside an inner edge d of the ring-shaped member b by fusion adhesion or through an adhesive agent.
If, in order to tear the closure member a open, the pulling tab e is held between one's fingers and is pulled upwards in relation to the closure member a, an initial stage of a broken opening of the closure member a is made at a portion corresponding to the initial end g of an interconnection portion between the pull-opening member f and the closure member a. If the pulling tab e is further pulled upwards together with the pull-opening member f, the tearing of the closure member a is guided along a guide edge h of the pull-opening member f to reach the inner edge d of the ring-shaped member b, and at the same time the tearing is made along an inner side edge i of the pull-opening member f with an X point serving as a starting point of the tearing.
If the lifting of the pulling tab e is further continued, the tearing which has reached the edge d is advanced along the inner edge d, and at the same time the tearing made along the inside edge i is advanced until it goes nearly half round. However, the advancing of the tearing is discontinued when the center region of the closure member a is loosened or slackened. Accordingly, the subsequent tearing stress is concentrated only on the portion extending along the inner edge d. As a result, only the tearing along the inner edge d is continued to the end, so that a full opening of the container can be obtained.
However, when the pulling direction of the pulling tab e connected to the initial end of the pull-opening member f is not proper or when there is a poor adhesion to the closure member a at part of the inner side edge i of the pull-opening member f, it often happens that tearing along the inside edge i cannot be made smoothly or that the tearing advance is discontinued before it goes half way around the closure member. Consequently, there cannot be obtained a desired sufficient slackening of the closure member a. Accordingly, the tearing stress does not concentrate only on the opening edge d, and as a result a tearing of the closure member a is made at an intermediate area between the inner edge d and the pull-opening member f, and a piece of the closure member a remains unremoved at such a portion near the inner edge d' as the tearing is advanced about 180.degree. turning degrees from the initial tearing opening portion as shown by imaginary lines in FIG. 7.